Re: Will SETI@home roast my CPU?




Phil H wrote:

There appears to be a misunderstanding here.

When any PC (or laptop) is switched on and working the energy and heat
dissipation by the CPU is not affected by applications. The CPU is
continuosly running the operating system when it is not executing
application code. The activity of the CPU at a physical level is the
same either way.

The only way the SETI@HOME application can make a difference is if it
prevents the system hybernating or going into some power saving mode
during idol time, but that usually only happens when there is no user
activity. At all other times the machine is either up and running
normally or it is not. If that causes temperature stability or
overheating then the machine is faulty and S@H won't make any
difference.

Speaking as an electronics engineer with experience in this area...

The above is incorrect, and has been incorrect for many years.
It was correct back when we were all running Apple IIs and
Commodore 64s with NMOS processors, but modern processors are
another matter. There are two factors that cause CPU temperatiure
to vary with load. The first is the basic physics of CMOS logic;
maximum heat generated at maximum switching frequency. A idle
CPU has large sections that are sitting at 1 or 0 and thus not
generating much heat. Add a heavy load and those sections start
switching at a rate of billions of 0-1 or 1-0 transitions per
second, and thus generating heat. The second factor is the fact
that CPU designers put in additional power saving features, with
some sections running at slower speeds and some sections being
powered down when not in use.

Getting back to the original question, there is another factor
to consider; temperature cycling. Yes, electronics likes to be
cool, but elecronics also likes being at a constant temprature.
It is not clear whether running SETI@Home 27/7 and thus keeping
the CPU at a steady higher teperature is better or worse than
letting it cycle from cold to hot to cold. Either way, you will
almost certainly buy a new computer long before the time when
the CPU goes bad from either factor.

What I do know is the obvious fact that if SETI@Home was damaging
CPUs everyone in this newsgroup would be talking about it.


--
Guy Macon
<http://www.guymacon.com/>

.

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